NO313600B1 - A method for recovering a rotary pump from a well channel and a rotary pump unit for detachable coupling with a drive - Google Patents

Description

The present invention relates to a method for retrieving a rotary pump from a well channel while leaving the pump drive in the well channel and a rotary pump unit for releasable connection with a drive.

Subsurface fluids, such as oil, gas and water, are often pumped or "lifted" from the well by the operation of fire pumps, e.g. submersible electric pump systems. These pump systems usually include an elongated electric motor that is installed in the well channel for rotation of a multi-stage centrifugal pump. Although centrifugal pumps are widely used for extracting underground fluids, such centrifugal pumps have difficulty in lifting viscous fluids, for example from Southern California, and fluids with relatively high concentrations of sand or other abrasive materials, e.g. from the tar sands area of Alberta, Canada. There is therefore a need for a well pump that can lift such fluids.

Among other things, US 4,171,934 should be highlighted from the prior art. This document deals with the assembly of a pump and associated electric motor where the rotatable part of the motor at its upper end has an anchoring head to be able to retrieve the pump and motor to the surface. Furthermore, EP 0704599 A deals with a downhole pump assembly which can be suspended by means of lugs in grooves in a well pipe, and where the lugs can be pressed in to release the pump and recover that surface.

To remedy the problem of extracting viscous fluids and fluids with relatively high sand concentrations, a Moineau pump or a progressive chamber pump can be used. Conventional installations of such pumps have the drive mechanism located at the ground surface. A rod string is used as a drive shaft inside the production pipe string. In wells that are inclined and/or emit abrasive materials, the rotating string can cause wear on the production tubing string. The frequent replacements of the production pipe string are very expensive and can prevent the operation of a well according to the bill.

It is a problem with progressive chamber pumps that the seal arranged between rotor and stator wears out, which reduces the pump's performance, so that in the end it does not pump fluid and therefore has to be retrieved periodically from the well channel. As the pump is permanently connected to the drive mechanism in the well, the entire latter mechanism must also be retrieved together with the pump, which is a time-consuming and relatively expensive process that requires the use of an overhaul rig. The well-installed drive mechanisms have effective lifetimes that are many times longer than that of the progressive chamber pump, and there is therefore a need for a method and apparatus for retrieving exclusively the pump, while the drive mechanism is left in the well channel. With such a method, the size of the traction unit can be reduced with consequent time and money savings.

A previously mentioned problem in connection with the use of progressive chamber pumps is that the seal between the rotor and the stator is subject to wear, whereby the pump's performance is reduced until the fluid pumping ceases. The pump must therefore be retrieved periodically from the well channel. The pump has previously been permanently connected to the well driver, which therefore had to be retrieved in its entirety together with the pump. The relevant inventors have developed methods with associated equipment for dismantling the pump from the drive and reassembling it while both are in a well channel, with subsequent retrieval of the pump to the surface.

The purpose of the invention is to remedy the above-mentioned deficiencies and meet the described needs. In particular, the invention relates to a method and associated apparatus for installing in and retrieving a rotary pump from a well channel while leaving the pump's drive mechanism in the well channel. A gripping mechanism is lowered into the well channel by means of a cable or a hose pipe, and connected to the rotary pump. Locking mechanisms that connect the rotary pump demountably with the pump driver are released by pulling on the cable or hose pipe or by applying hydraulic pressure. The gripping mechanism and the pump are then retrieved from the well channel, while the drive unit is still suspended in the channel.

As briefly mentioned in the above, the invention relates to a method and associated apparatus for installing in and retrieving a rotary pump from a well channel while leaving the pump driver in the well channel. In a preferred version of the method according to the invention, a gripping mechanism is lowered into a well channel by means of a cable or pipe hose and connected to the rotary pump which is suspended in the well channel. Locking mechanisms that connect the rotary pump demountably with the pump driver are released by pulling on the cable or pipe hose or by applying hydraulic pressure. The gripping mechanism and the pump are then recovered from the well channel, while the drive unit is still suspended in this.

The mentioned rotary pump can be of any type used for extracting well fluids, e.g. a centrifugal pump, progressive chamber pump, vane pump, turbine, gear pump and the like. With regard to the following description, it is assumed that the rotary pump is in the form of a progressive chamber pump.

In the following description, the term "drive unit" is used to refer to the well assembly that supplies rotational drive power to the pump. This drive unit includes at least one oblong submersible electric motor, and will usually also include one or more oil-filled motor protectors which will be known to those skilled in the art. If a progressive cam pump with a submersible electric motor is used, it will be preferable to engage a reduction gear to reduce the pump speed and increase the torque transmitted to the pump. Together with a reduction gear, the use of a joint coupling, a flexible rod or a joint unit for limiting the lateral displacement of the drive shafts is preferred. Such a preferred joint unit is described in US patent 5,421,780.

In the following description, the term "grabbing mechanism" is used for any lowered positioning nipple and/or fishing tool with tabs, hooks, grappling hooks, bar parts or the like which is suspended by a conventional wire, cable, continuous or articulated suction rod or pipe hose and is releasably connected to an external the portion of a cam on or adjacent to the pump, or an internal recess on or adjacent to the pump. Such devices will be known to those skilled in the art and are widely marketed by divisions of Camco Products & Services Company, Dowell Schlumberger and Baker Hughes Incorporated.

The gripping mechanism for picking up the pump is preferably placed or lowered into the well channel, handled or turned and raised or pulled up from the well channel at the end of a conventional wire, braided multi-part cable, continuous or articulated suction rod or tubing. The weight of the pump can exceed the load limit for conventional wire, and the use of pipe hose is not necessarily the most economically advantageous due to the relatively high rigging costs, and braided multi-part cable is therefore most preferred for deploying the gripping mechanism.

The method according to the invention is characterized by the independent claim 1, while preferred embodiments are characterized by the non-independent claims 2-19.

The device according to the invention is characterized by the independent claim 20, while preferred embodiments are characterized by the non-independent claims 21-40.

Reference is made to the drawings, in which:

Fig. 1 shows a side view, partly in section, of a pump which is connected to an electric motor and suspended in a well channel, in accordance with a preferred method according to the invention. Fig. 2 shows a vertical section of a preferred version of the pump unit according to the invention. Fig. 3 shows a vertical section of another preferred version of the pump unit according to the invention. Fig. 1 shows a well 10 for extracting subsurface fluids, such as oil, gas and/or water from one or more subsurface formations 12. The well 10 includes a casing string 14 which is connected at the ground surface to a wellhead and a production tree 16, with valves and pipelines, as known to those skilled in the art. A submersible electric pump system 20 is suspended in a production pipe string 18 in the well channel 10. The pipe string 18 can be in the form of conventional jointed pipe sections or pipe hose, if desired. The pump system 20 can also be cable-suspended if desired. In connection with the present description, the pump system 20 is described as a Moineau pump or a progressive chamber pump 22 which is connected in an upper part to the pipe string 18 for transferring the underground fluids to the field surface. The lower end of the pump 22 is connected to one or possibly several reduction gears 24, one or possibly several oil-filled electric motor rotors 26, and below the motor guard 26

one or more oblong and submersible electric motors 28 are connected. The motor 28 receives electrical current through a cable 30.

As known to those skilled in the art, fluids from the underground formations 12 will flow in through openings or perforations (not shown) in the well pipe 14, to be transported along the outer wall of the electric motor 28 and flow in, through one or more openings 32, in a lower part of the pump 22. The fluids entering through the opening(s) 32 are transported upwards through the pump 22 by rotation of the helical rotor (not shown) in the corresponding helical stationary stator (not shown) and are continued upwards through the production pipe string 18 to the field surface.

It is in fig. 2 shows a preferred method with associated apparatus, where a progressive chamber pump 22 is installed in a pipe stem 34. The pump 22 is movable in the longitudinal direction in a longitudinal and continuous channel in the pipe stem 34, as described in more detail below. A first or lower end of the pipe stem 34 is threadedly connected to the outer housing of the reduction gear 24, the optional motor guard 26 or the motor 28. The second or upper end of the pipe stem 34 is threadedly connected to the lower end of the production pipe string 18.

It appears from fig. 2 that the pump 22 comprises a stationary stator 38 which accommodates a helical rotatable rotor 40. The first or lower end of the rotor 40 includes a drive coupling 42 which may be in the form of a conventional drive transmission coupling which permits longitudinal sliding or movement, but a knurled coupling device is preferred. A knurled conical shaft 44 extends in particular from the reduction gear 24, the motor guard 26 or to the motor 28, depending on which of these is located closest to the pump 22. This knurled shaft 44 is received in a corresponding grooved bore 46 in an extended end of the shaft 4 8 which is connected to the rotor 40.

The other or upper end of the rotor 40 includes a flange 50 which is fitted in an annular recess 52 in the pump stator housing or in a cylindrical fitting 54 which is connected to the other or upper end of the pump 22. The flange 50 prevents the rotor 40 from falling out from the stator 3 8 when the pump 22 is in operation and while it is being dismantled and installed in the well channel 10. The flange must run between the upper and the lower boundary zone and thereby prevent rubbing against these during normal rotation. The second or upper end of the rotor 40 may also include a flanged neck portion for interaction with a conventional retrieval or fishing tool, as will be known to those skilled in the art.

A cylindrical cap 56 is threadedly or stud-connected to the other or upper end of the pump 22 or cylindrical adapter 54, and arranged for coupling a retrieval tool (not shown) to the pump 22, for retrieval thereof. The cap 56 may be in the form of a conventional wire or fishing locating nipple (or locking stem) or similar device as will be known to those skilled in the art. In the embodiment shown in fig. 2, the cap 56 is firmly connected by threads, studs or welding to the second or upper end of the pump 22 or the cylindrical fitting part 54, and includes a number of sealing rings 58 which seal against an inner wall portion of the channel 36 in the pipe stem 34. At the second or upper end of the cap 56 there is also an annular recess 60 for receiving the retrieval tool, as described in more detail below.

In order to prevent the pump 22 from moving in the longitudinal direction (ie up and down) in the pipe stem 34 and/or from turning or rotating in relation to the pipe stem 34, locking mechanisms are arranged in the cap 56, the pipe stem 34 and/or the pump 22. The locking mechanisms can be operated electrically, pneumatically, hydraulically or mechanically. In one version, the locking mechanisms consist of breaking pins that are broken or released by longitudinal and/or rotational movement. In the preferred embodiment according to fig. 2, the locking mechanisms comprise a number of spring-loaded tabs or lugs 62 which are held in an extended position by mutual movement of the cap 56 and the pipe stem 34, by the weight of the pump 22 or in another commercially known manner. When they are placed in the cap 56, the cams 62 are received in radially separated openings 64 in the tube stem 34, and when they are placed in the tube stem 34, the cams 62 are received in openings 64 in the cap 56. In the case of conventional turning movement, vibration, longitudinal movement upwards or downwards or a combination of these, which will be known to those skilled in the art, the cams 62 are retracted to allow longitudinal and/or rotational movement of the pump 22 in relation to the pipe stem 34.

In an alternative version, the cams 62 are used exclusively to limit the longitudinal movement of the pump 22 in relation to the pipe stem. Rotational movement of the pump 22 is limited by a rib (not shown) which projects outwards from a lower outer wall portion of the pump housing, and which cooperates with one or more ribs (not shown) which are included in or are attached to the inner wall of the pipe stem 34.

Fig. 3 shows a preferred alternative version according to the invention, where the cams 62 are retracted by the transmission of electric current or hydraulic pressure from a control line 66 which extends to the surface. Furthermore, the knobs 62 according to fig. 3 is retracted or extended by transfer, to the annulus between the pipe stem 34 and the well pipe 14, of a fluid pressure that exceeds a predetermined limit, or by creating a pressure difference that exceeds a predetermined limit, between the pipe stem-well pipe annulus and the interior of the pipe string 18.

When the submersible pump system is installed in the well channel 10, the entire pump unit is assembled at the surface and lowered into the well channel 10, suspended by cable or in the pipe string 18, with the power cable 30 attached on the outside, as known to those skilled in the art. If and when the pump 22 is to be retrieved, the motor 28 is stopped and a gripping mechanism is lowered into the well channel 10 by means of a wire, a braided multi-part cable, a continuous or articulated suction rod or a pipe hose. The gripping mechanism (not shown) is received in the annular recess 60 and is handled to release the locking mechanisms. In the embodiment according to fig. 2, only longitudinal or upward movement of the cap 56 in relation to the pipe stem 34, which is firmly connected to the pump driver, will cause the cams 62 to retract. With upward movement of the cap 56, the pump 22 will also be pulled out from the pipe stem 34 and the knurled shaft 44 retracted from the grooved bore 46. Both the gripping mechanism and the cap 56 and the pump 22 are retrieved to the surface. The pump drive is left suspended in the well channel 10, because the pipe stem 34 is firmly connected between the pipe string 18 and the reduction gear 24, the motor protection 26 and/or the motor 28.

In the preferred version according to fig. 3, electrical current or hydraulic pressure is supplied to the cams 62 through the control line 66, or the desired annulus pressure difference is created for retraction of the cams 62.

The reduction gear 24 and/or a motor guard 26 can, if desired, be permanently connected to the other end of the pump rotor 40, with the knurled coupling 42 placed between the reduction gear 24 and a motor guard 26 or, if two motor guards are in use, between the first and the second motor guard 26 and/or the pump 22 which is firmly connected to the pipe string 18 through the pipe stem 34. In this way, the pump 22, the reduction gear 24 and possibly a motor guard 26 can be easily retrieved from the well channel while the other parts of the drive mechanism are left in the well channel 10 .

When the pump 22 is to be reinstalled in the well channel 10, the gripping mechanism is releasably connected to the cap 56 and/or the pump 22, and the latter is lowered into the well channel 10. The lower end of the rotor 40 is connected to the drive coupling 42. This drive coupling 42 includes a flat part of larger outer diameter. As the unit is lowered into the well channel, the larger diameter flat portion passes through the longitudinal channel 36 below which an inclined portion extends to a section of reduced diameter slightly larger than the drive coupling 42. As it passes through the inclined portion, the drive coupling 42 is centered in alignment with the fluted shaft 44. The bore grooves and the shaft flutes are inclined, so that when they move downwards, they will turn slightly and interlock. On further lowering of the unit, the drive coupling 42 section of the large diameter will pass completely through and clear of the portion of the reduced diameter. The drive coupling can thereby oscillate with the pump rotor to the required extent. When the bore 46 and the shaft 44 are matched, outer or protruding grooves on the other or lower end of the pump will be matched with inner grooves on the pipe stem 34 . The bore grooves and the lower pump housing grooves are conical, and during downward relative movement will turn slightly and interlock. A step on the shoulder portion 68 is brought into contact with the shoulder portion 70 and prevents further downward movement.

A second embodiment has grooves at the bottom of the drive coupling 42. In this version, a flexible drive mechanism is included which must be left together with the drive unit in the well channel. The lower end of the rotor 40 is connected to the drive coupling 42 which includes a surface portion of larger outer diameter. When the assembly is lowered into the well channel, said surface will pass through the longitudinal channel 36 which, through an inclined section below, transitions to a section of reduced diameter, which is somewhat larger than the drive coupling 42. As it passes through the inclined section, the drive coupling 42 is centered in alignment with it internal fluted shaft 44. As previously described, the bore grooves and the shaft flutes run obliquely so that they will turn slightly and interlock during downward relative movement. On continued lowering of the assembly, the larger diameter section of the drive coupling 42 will pass completely through and clear of the reduced diameter section. The drive coupling can thereby oscillate with the pump rotor to the required extent. When the bore and the shaft are matched, the external or projecting rifle, which is connected to the other or lower end of the pump, will fit into the internal groove in the pipe stem 34. The bore groove and the pump housing rifle are inclined, so that during downward relative movement will turn slightly and connect.

When the pump 22 is almost inserted into the pipe stem 34, the spring-loaded cams 62 are brought into contact with the upper end of the pipe stem 34, and pushed inward to a retracted position. Alternatively, the cams 62 can be retracted at the surface and held in this position until they are released at or near the openings 64. During continued lowering of the pump 22, the spring-loaded cams 62 will extend towards and into the openings 64 and thereby lock the pump unit in the pipe stem 34 against longitudinal and/or rotational movement, until the pump 22 is to be retrieved again.

With this retrieval method and the associated apparatus, the control line 66 (if used) is isolated from moving parts, so as not to be damaged as sometimes occurs when pumps and drives are removed from the well, because the cable 30 and the control line 66 are located outside the pipe stem 34 and the pipe string 18 .

As can be seen from the above description, the present invention will make it possible to recover a pump in a relatively quick and cheap way without the need for recovery of the pump's drive mechanism with all the accompanying costs and risk of damage.

Claims (34)

1. Method for retrieving a rotary pump (22) from a well channel while leaving the pump driver (24,28) in the well channel, characterized by (a) lowering a gripping mechanism into the well channel, and connecting the gripping mechanism with a pump (22) which is suspended in the well channel, (b) releasing the locking mechanisms (62) which releasably connect the pump to the pump driver, and (c) extracting the gripping mechanism and the pump from the well channel. 2. Method in accordance with claim 1, characterized in that the locking mechanisms (62) are further arranged to counteract longitudinal movement of the pump (22) in relation to the pump driver (24,28), and where the locking mechanisms are released by longitudinal movement of the gripping mechanism. 3. Method in accordance with claim 1, characterized in that the locking mechanisms (62) are further arranged to counteract longitudinal movement of the pump (22) in relation to the pump driver (24,28), and where the locking mechanisms are released by rotational movement of the gripping mechanism. 4. Method in accordance with claim 1, characterized in that the locking mechanisms are released when hydraulic pressure is applied. 5. Method in accordance with claim 1, characterized in that the gripping mechanism is lowered by means of a cable, that the locking mechanisms are released by pulling the cable and that the cable is subsequently withdrawn. 6. Method in accordance with claim 1, characterized in that the locking mechanism is lowered by means of the cable, that the locking mechanisms are released by applying a hydraulic pressure and that the cable is subsequently withdrawn. 7. Method in accordance with claim 5, characterized in that the cable consists of a wire. 8. Method in accordance with claim 5 or 6, characterized in that the cable is of the braided multipart type. 9. Method in accordance with one of claims 5-8, characterized in that the locking mechanisms comprise force-affected elements (62) which, in the extended position, prevent longitudinal movement of the pump in relation to the drive mechanism. 10. Method according to one of claims 5-9, characterized in that the pump is placed in a pipe stem (34) which is connected at one of its ends to the pump drive (24,28). 11. Method in accordance with claim 10, characterized in that the other end of the pipe stem (34) is connected to a production pipe string (18) which is suspended in the well channel. 12. Method in accordance with claim 10 or 11, characterized in that the locking mechanisms (62) releasably connect the pump to the interior of the pipe stem (34). 13. Method according to one of claims 5-12, characterized in that a drive shaft (42) is arranged at one end of the pump and is releasably connected to a drive shaft (44) in the pump drive. 14. Method in accordance with claims 10 and 13, characterized in that the pump drive shaft (42), when the pump is retrieved from the pipe stem (34), is retracted in the longitudinal direction from connection with the pump drive's drive shaft (44). 15. Method according to one of claims 5-14, characterized in that the pump (22) is of a progressive chamber type. 16. Method in accordance with claims 6-14, characterized in that the cable is in the form of a logging wire. 17. Method in accordance with claim 6, characterized in that the locking mechanisms comprise force-affected elements (62) which, in the extended position, prevent longitudinal and rotational movement of the pump in relation to the drive mechanism. 18. Method in accordance with claim 6, characterized in that the locking mechanisms comprise pistons (62) which are withdrawn when hydraulic pressure is applied. 19. Method in accordance with claim 18, characterized in that the pistons (62) are withdrawn by applying hydraulic pressure through a control line (66) which extends to the surface. 20. Rotary pump unit for releasable connection with a drive unit (24,28), characterized by a pipe stem (34) with a device at a first end for connection to the drive unit (24,28) down in the well, a rotary pump (3 8,40) which is installed in the pipe stem (34), a device (46,48) on a first end of the rotary pump for releasable coupling to a drive shaft (44) in the drive train, and devices (56,60) on a second end of the rotary pump for releasable coupling with a retrieval tool. 21. Rotary pump unit in accordance with claim 20, characterized in that the pump is of a progressive chamber type. 22. Rotary pump unit in accordance with claim 20 or 21, characterized in that a second end of the pipe stem (34) is arranged for connection with a production pipe string. 23. Rotary pump unit in accordance with one of claims 20-22, characterized in that the first end of the pipe stem (34) is connected to an outer housing for the drive mechanism (24,28). 24. Rotary pump unit in accordance with one of claims 20-23, characterized in that the detachable coupling device on the first end of the rotary pump is in the form of a spline shaft (44) which originates from the drive which is inserted in a spline bore (46) in a shaft (42) which emanates from the rotary pump. 25. Rotary pump unit in accordance with one of claims 20-24, characterized in that locking means (62) are arranged at the other end of the rotary pump which releasably prevent longitudinal movement of the pump in relation to the pipe stem (34). 26. Rotary pump unit in accordance with one of claims 20-24, characterized in that locking means (62) are arranged at the other end of the rotary pump which releasably prevent turning movement of the pump in relation to the pipe stem (34). 27. Rotary pump unit in accordance with one of claims 20-26, characterized in that, at the other end of the rotary pump, there are locking mechanisms' (62) which, in the extended position, prevent longitudinal movement of the rotary pump in relation to the pipe stem (34) . 28. Rotary pump unit in accordance with claim 27, characterized in that the locking mechanisms (62) are retracted by pulling the retrieval tool. 29. Rotary pump unit in accordance with claim 27, characterized in that the locking mechanisms (62) are retracted by the supply of hydraulic pressure through a control line (66) which extends to the surface. 30. Rotary pump unit in accordance with claim 20, characterized in that the drive comprises a submersible electric motor (28), that the rotary pump (38, 40) is placed in the pipe stem which is connected to the drive, and devices (44, 46) which releasably connect the rotary pump with the drive unit, as well as locking means (62) which releasably connect the rotary pump to the pipe stem. 31. Rotary pump unit in accordance with one of claims 20-30, characterized in that the retrieval tool is lowered on a cable. 32. Rotary pump unit according to one of claims 20-30, characterized in that the recovery tool is lowered onto a braided multi-part cable. 33. Rotary pump unit in accordance with one of claims 20-30, characterized in that the retrieval tool is lowered onto a continuous or articulated suction rod. 34. Rotary pump unit ;i, according to one of claims 20-30, characterized in that the recovery tool is lowered onto a pipe hose.